Amanda E. Semper

Dendritic cells in normal and asthmatic airways: expression of the α subunit of the high affinity immunoglobulin E receptor (FcεRI‐α)

Background Immunoglobulin E (IgE) plays an important role in asthma, with total serum IgE levels closely related to both clinical expression of the disease and airway hyperresponsiveness. IgE binds to a high affinity cell‐surface receptor (FcεRI) which is present on mast cells and which has also recently been demonstrated on cutaneous dendritic cells. If pulmonary dendritic cells were also able to express this receptor, this would have important implications with regard to their potential role in asthma.

Cytokine profiles of BAL T cells and T‐cell clones obtained from human asthmatic airways after local allergen challenge

Background: This study assessed the heterogeneity of cytokine expression in asthma before and after local allergen challenge.

Dendritic cells in normal and asthmatic airways: Expression of the alpha subunit of the high affinity immunoglobulin E receptor (FC epsilon RI-alpha)

BACKGROUND Immunoglobulin E (IgE) plays an important role in asthma, with total serum IgE levels closely related to both clinical expression of the disease and airway hyperresponsiveness. IgE binds to a high affinity cell-surface receptor (Fc epsilon RI) which is present on mast cells and which has also recently been demonstrated on cutaneous dendritic cells. If pulmonary dendritic cells were also able to express this receptor, this would have important implications with regard to their potential role in asthma. OBJECTIVES The aims of the study were to investigate the expression of the alpha subunit of the high affinity IgE receptor (Fc epsilon RI-alpha) in normal and asthmatic airways, and to analyse its cellular provenance with particular emphasis on the dendritic cell. METHODS Bronchial biopsy specimens were obtained using fibreoptic bronchoscopy from 10 atopic asthmatics and nine non-atopic non-asthmatic control subjects. Specimens were processed into glycolmethacrylate resin and analysed by immunohistochemistry using specific monoclonal antibodies against Fc epsilon RI-alpha, and against tryptase and CD1a, markers for mast cells and dendritic cells, respectively. RESULTS The numbers of dendritic cells were significantly higher in the airways of asthmatics compared with those of control subjects (P < 0.02). Analysis of sequential sections revealed that the alpha subunit of Fc epsilon RI was localized to both mast cells and dendritic cells. The proportion of dendritic cells expressing Fc epsilon RI-alpha was significantly increased in the asthmatic group (P < 0.003). CONCLUSION These results support the hypothesis that dendritic cells play an important role in allergic asthma although the functional significance of Fc epsilon RI-alpha expression needs further investigation.

Activation of human dendritic cells by the PorA protein of Neisseria meningitidis

The major porin proteins present in the outer membrane of Neisseria meningitidis, the causative agent of life‐threatening meningitis and septicaemia, are believed to have potent immunostimulatory effects. In this study, the interactions between human monocyte‐derived dendritic cells (mo‐DC) and the PorA porin were investigated, in order to reveal the role of this protein in promoting innate and adaptive immune responses. Recombinant (r)PorA induced mo‐DC maturation, as reflected by reduced receptor‐mediated endocytosis, increased production of the chemokines IL‐8, RANTES, MIP‐1α and MIP‐1β and augmented expression of the surface markers CD40, CD54, CD80, CD86 and major histocompatibility complex class II molecules. However, rPorA induced either low level or no significant secretion of pro‐inflammatory cytokines from mo‐DC. The protein potently augmented the capacity of mo‐DC to activate both allogeneic CD4+ memory T‐cells and CD4+RA+ naïve T‐cells. In addition, rPorA appeared to inhibit the production of IL‐12p70 that follows from the interaction between CD40 on the mo‐DC and CD40‐ligand on T‐cells, thereby directing T‐cell differentiation towards a Th2 type response. These data demonstrate that PorA is involved in DC activation and in influencing the nature of the T‐helper immune response, which are important properties for generating antibody responses required for protective immunity against meningococci and for determining the immuno‐adjuvant effects of this protein.

Activation of human dendritic cells is modulated by components of the outer membranes of Neisseria meningitidis

ABSTRACT Neisseria meningitidis serogroup B is a major cause of life-threatening meningitis and septicemia worldwide, and no effective vaccine is available. Initiation of innate and acquired immune responses to N. meningitidis is likely to be dependent on cellular responses of dendritic cells (DC) to antigens present in the outer membrane (OM) of the meningococcus. In this study, the responses of human monocyte-derived DC (mo-DC) to OM isolated from parent (lipopolysaccharide [LPS]-replete) meningococci and from a mutant deficient in LPS were investigated. Parent OM selectively up-regulated Toll-like receptor 4 (TLR4) mRNA expression and induced mo-DC maturation, as reflected by increased production of chemokines, proinflammatory cytokines, and CD83, CD80, CD86, CD40, and major histocompatibility complex (MHC) class II molecules. In contrast, LPS-deficient OM selectively up-regulated TLR2 mRNA expression and induced moderate increases in both cytokine production and expression of CD86 and MHC class II molecules. Preexposure to OM, with or without LPS, augmented the allostimulatory properties of mo-DC, which induced proliferation of naive CD4+ CD45RA+ T cells. In addition, LPS-replete OM induced a greater gamma interferon/interleukin-13 ratio in naive T cells, whereas LPS-deficient OM induced the reverse profile. These data demonstrate that components of the OM, other than LPS, are also likely to be involved in determining the levels of DC activation and the nature of the T-helper immune response.

Expression of the High Affinity Receptor for Immunoglobulin E (IgE) by Dendritic Cells in Normals and Asthmatics

Immunoglobulin E (IgE) plays an important role in the pathophysiology of asthma and other allergic diseases. In mucosal tissues, IgE binds to specific receptors on the surface of mast cells, eosinophils and other inflammatory cells providing an important trigger mechanism for the release of inflammatory mediators.

Cellular Changes 24 Hours after Endobronchial Allergen Challenge in Asthma

Asthma Eosinophils Lymphocytes Endobronchial challenge Histology Correspondence to: Dr. A.J. Frew, University of Southampton, Room CD 139, Level D, Centre Block, Southampton General Hospital, Tremona Road, Southampton SO16 6YD (UK) Local endobronchial allergen challenge allows a high dose of allergen to be delivered to a single airways segment to study the release of spasmogenic mediators [1] and recruitment of T cells and other leucocytes in small blood vessels in the subjacent bronchial mucosa [2], in comparison to matched control sites. Six hours after challenge, we found an increased number of eosinophils and neutrophils with up-regulation of the endothelial adhesion molecules ICAM-1 and Eselection [3]. We have extended these studies to address the cellular changes 24 hours after local allergen exposure. caine. Endobronchial challenge was performed in the medial segment, right middle lobe with 20 ml of prewarmed allergen solution, the concentration used being calculated by skin test titration. Control challenge was performed with 20 ml saline diluent in the anterior segment, right upper lobe. The airway was observed for 5 min to confirm bron-choconstriction. A second bronchoscopy was performed with identical premedication 24 h later. Bronchoalveolar lavage (BAL) was performed in each of the challenged segments with 120 ml isotonic warm saline and four mucosal biopsies were obtained from each segment. Mucosal biopsies were processed into glycol methacrylate and stained with monoclonal antibodies and an indirect peroxidase technique. BAL cells were processed for flow cytometry and in a small number of cases, samples were studied by PCR for cytokine transcription.